1. Field of the Invention
The present invention generally relates to semiconductor processing. More particularly, the invention relates to an apparatus for performing cyclical deposition processes in semiconductor substrate processing systems.
2. Description of the Related Art
An atomic layer deposition (ALD) process is a cyclical deposition method that is generally used for depositing ultra-thin layers (e.g., mono-layers) over features of semiconductor devices having a high aspect ratio, i.e., a ratio of the depth of a feature to the smallest width of the feature.
The ALD process utilizes a chemisorption phenomenon to deposit mono-layers of reactive precursor molecules. During the ALD process, reactive precursors are injected, in the form of pulsed gases, into a deposition chamber in a predetermined cyclical order. Each injection of a precursor provides a new atomic layer on a substrate that is additive to or combines with the previously deposited layers. Injections of individual precursor gases generally are separated by injections of a purge gas or, in other embodiments, the purge gas may be flown continuously into the deposition chamber. The purge gas generally comprises an inert gas, such as argon (Ar), helium (He), and the like or a mixture thereof. During the ALD process, the deposition chamber is also continuously evacuated to reduce the gas phase reactions between the precursors.
There are many challenges associated with ALD technique that affect the film properties and costs of operation and ownership. For example, unwanted gas phase reactions between precursors within the process chamber of the prior art may cause contamination of deposited films and require frequent cleaning of the chamber, thus decreasing productivity of the ALD process.
Therefore, there is a need for an improved apparatus for performing cyclical deposition of thin films during fabrication of semiconductor devices.